Piezoelectric energy harvesting and wireless sensing powered by non-harmonic motion

Abstract

This thesis focuses on the design of non-harmonic motion-powered wireless sensing systems using piezoelectric energy harvesting. Most of the published work on the topic of inertial energy harvesting focussed on the analysis and design of the energy harvester modules only. A limited amount of work has involved the implementation of energy harvesters into a wireless sensing system, which is an important application of energy harvesters. This project presents an approach to simplify the design of a wireless sensing system so that a single piezoelectric energy harvester can be used as the power supply. A piezoelectric device structure with impulse output was proposed and an equivalent circuit model was built to simulate the performance. Both a large-scale and a small-scale piezoelectric pulse generator were produced for experimental demonstration, based on the proposed structure. A passive pre-biasing mechanism was introduced to improve the performance of the pulse generator, and the improvement was demonstrated by comparing the outputs of the prototypes in the pre-biased case to the outputs in the unbiased case. The comparison results showed that the output energy was increased by 38% for the large-scale prototype and 76% for the small-scale prototype. Load transmission circuits, suitable for the piezoelectric pulse generator, were discussed and simulated, and an impulse-powered transmitter circuit based on the Colpitts oscillator was built, which could encode the signal from a sensor by frequency modulation. By combining the piezoelectric pulse generator module and the impulse-powered transmitter module together, a fully functional piezoelectric system was achieved, for the first time, allowing instantaneous wireless monitoring of signals from a passive sensor using frequency modulation.Open Acces